BMI Calculator

Metric and Imperial/US units

Recommendation of weight limits for underweight, overweight and obese

What is BMI?

Body mass index (BMI), or Quetelet Index, is an attempt to estimate the mass of tissue (muscle, fat and bone)
in an individual to identify their fitness level. Although proposed in 1830 by Adolphe Quetelet as the eponymous Quetelet Index,
it wasn't until 1972 that the now popular term BMI came into existence. It is measured simply as a ratio of weight (in Kgs) to the
square of height (in metres). See our detailed table for information on the fitness categories based on BMI.

Factoid

To discourage anorexia, many countries, including France, Israel, Italy and Spain have
banned models below a BMI of 18.5 from the fashion shows.

What do the BMI scores mean?

Fitness categories based on Body Mass Index (BMI), as published by World Health Organization (WHO)

Fitness Category

BMI

BMI Prime

Very severely underweight

less than 15

less than 0.60

Severely underweight

from 15 to 16

0.60 to 0.64

Underweight

from 16 to 18.5

from 0.64 to 0.74

Normal or Healthy

from 18.5 to 25

0.74 to 1.0

Overweight

25 to 30

1.0 to 1.2

Moderately obese

30-35

1.2 to 1.4

Severely obese

35 to 40

1.4 to 1.6

Very severely obese

Over 40

over 1.6

The ABSI scores should be compared with the average scores of the people of same age and gender.
Significantly higher scores indicate higher health risks.

Individuals categorized as overweight or obese according to BMI scores as typically considered to be
at a higher risk for many life threatening diseases such as coronary heart disease, Dyslipidemia, Type 2 Diabetes,
Gallbladder disease, Hypertension, Osteoarthritis, Sleep Apnea, and several forms of cancer, including endometrial, breast,
and colon cancer.

Factoid

Interestingly, recent research has shown that overweight individuals, or those having a
BMI score between 25 and 29.9, have a lower overall mortality than all other categories.

This obesity-mortality paradox is now driving research into novel alternative metrics
as well as to improve our understanding of what it really means to be obese.

Limitations of BMI

Among its many limitations, BMI does not scale well with height. For example, taller individuals typically
end up having a higher BMI score than their shorter counterparts with
similar health profile.

Similarly, BMI also ignores variation in physical characteristics, such as large or small frame size. For
example, the body fat percentage of a smaller framed person might be high but still not result in a high
BMI score. On the contrary, a large framed person, with lean body composition might still have a higher
BMI.

Also, the BMI score is independent of gender. It is well-known that men and women store body fat differently, and
that men typically need lower fat reserves than women. So for the same height and weight combination, and thereby same
BMI, two individuals can be drastically different in their health profiles, just because they belong to different genders.
It is interesting to note though that the World Health Organization (WHO) has not created gender-specific BMI fitness categories.

Thus, several in the research community have questioned the suitability of BMI as a fitness estimate.
Owning to these reasons, BMI can actually be quite inaccurate and misleading.

Better alternatives?

Body fat percentage is widely regarded as a better estimate of fitness, as gender-specific guidelines
are known.

Body mass index

The body mass index (BMI) or Quetelet index is a value derived from the mass (weight) and height of an individual. The BMI is defined as the body mass divided by the square of the body height, and is universally expressed in units of kg/m2, resulting from mass in kilograms and height in metres.
The BMI may also be determined using a table or chart which displays BMI as a function of mass and height using contour lines or colors for different BMI categories, and may use two different units of measurement.
The BMI is an attempt to quantify the amount of tissue mass (muscle, fat, and bone) in an individual, and then categorize that person as underweight, normal weight, overweight, or obese based on that value. However, there is some debate about where on the BMI scale the dividing lines between categories should be placed. Commonly accepted BMI ranges are underweight: under 18.5 kg/m2, normal weight: 18.5 to 25, overweight: 25 to 30, obese: over 30. . Read more...

For people who are considered obese (BMI greater than or equal to 30) or those who are overweight (BMI of 25 to 29.9) and have two or more risk factors, it is recommended that you lose weight. Even a small weight loss (between 5 and 10 percent of your current weight) will help lower your risk of developing diseases associated with obesity. People who are overweight, do not have a high waist measurement, and have fewer than two risk factors may need to prevent further weight gain rather than lose weight. Read more at nih ..

This calculator computes the body mass index and rates it appropriately for men, women, children, juveniles and seniors. The SBMI serves for this purpose - an index that has been newly developed especially for this calculator. Read more at smartbmicalculator ..

Fat-free mass is made up of muscles, tendons, bones, ligaments, connective tissue, blood, nerves, inner organs, and the like. All these structures are shaped according to their functions which stay more or less the same during life. Therefore, it is unlikely that their mass will change very much. However, bodybuilding is the exception that proves the rule. Read more at smartbmicalculator ..

About half of all the BMI records for the age of 20years are in the range of 20-24 in men and 19-23 in women. This range matches more or less the WHO definition of the normal weight. There is an upward shift of the observed "normal range" by about one BMI unit per life decade for both sexes up until age 60years, plus an additional unit per life decade in men between the ages of 20 and 40years. Above the age of 60, a plateau is reached for both sexes. Samples for ages of 65+ are too small to draw any valid conclusions. Read more at smartbmicalculator ..

Smokers tend to be slimmer than non-smokers, and quitters tend to gain weight. This is a well-known fact, and it is scientifically proven. Now, if you do statistics about BMI and health, you cannot just group people by their BMI and look for health outcomes. This is not possible because in the lower BMI groups you are likely to find more smokers than in the higher BMI groups. The more smokers in your statistics, the more likely you will see positive health outcomes in fat versus slim people. If you are not smoker-conscious, you may falsely conclude body mass to be beneficial. In fact, you have just found out that smoking kills. Read more at smartbmicalculator ..

Firstly, it takes age and sex into account, besides weight and height. Secondly, the SBMI is a purely comparative figure (without any physical units) on a scale of 70 points. And thirdly, the significance of the body weight for your health can easily be derived from the SBMI but not from the BMI: The weight-related health risk levels shown in green, yellow, orange and red (see the SBMI chart on the Results page), have 10/70SBMI points in each case. Read more at smartbmicalculator ..

Please remember, however, that this is only one of many possible ways to assess your weight. If you have any concerns about your weight, please discuss them with your physician, who is in a position, unlike this BMI calculator, to address your specific individual situation. Read more at bmi-calculator ..